The EGF receptor and neu receptor are tyrosine kinases regulated by their respective peptide growth factor ligands. The EGF and neu receptors are involved in stimulating mitogenic signal transduction pathways which cause proliferation of mammary carcinoma cells. The objective is to identify compounds and gene therapy approaches to inhibit receptor-mediated stimulation of mammary carcinoma cell growth. Designing mutant inhibitory genes in combination with pharmacological inhibitors of EGF/neu receptor functions are predicted to synergistically arrest mammary carcinoma cell growth. The approach is to use dominant negative mutants of proteins required for EGF/neu receptor signaling. Expression of these growth inhibitory genes in mammary carcinoma cells will be accomplished using adenovirus expression. The adenoviruses will encode cDNAs that express fusion proteins having Src homology (SH) domains 2 and 3 within their sequence that will disrupt binding and activation of phospholipase C-gamma, P13 kinase and the adaptor protein Grb2 that is involved in Ras activation. Other adenovirus vectors will encode proline-rich SH3 domain binding sequences or a dominant negative mutant Raf. Expression of these mutant proteins will be used to define dominant sites in the EGF/neu receptor signal transduction pathways that when disrupted strongly inhibit mammary carcinoma cell growth. Tyrosine kinase inhibitors, EGF receptor and neu receptor antibodies, and other pharmacological agents that inhibit EGF and neu receptor signal transduction will be used in combination with the inhibitory gene products. The goal is to translate the findings to an effective strategy to inhibit the growth of breast cancer cells in women.